Process for the hydrolytic hydrogenation of carbohydrates in an acid medium



p 1952 c. M. H. KOOL ETAL 2,609,399

PROCESS FOR THE HYDROLYTIC HYDROGENATION OF CARBOHYDRATES AN ACID MEDIUMFiled D60. 30, 1947 INVENTORS 6? h. 4 001 A. van We f BY L. Harfsfra ePatented Sept. 2, 1952 t PROCESS FOR THE HYDROLYTIO HYDRO GENATION OFCARBOHYDRATES: IN

ACID MEDIUM" Cornelis Martinus Hendrik l i ool, Hal-en, and HendrikAdriaan van Westen and Lenze Hartstra, Amsterdam, Netherlands, assignorsto Naamlooze Vennootschap W. 'A. Scholtens Chemische Fabrieken,Groningen, Netherlands, a corporation-of the Netherlands ApplicationDecemberBO, 1947, Serial No. 794,574

In the Netherlands September 30, 1943 1' The invention relates to aprocess for the hydrolytic hydrogenation of carbohydrates in an acidmedium, e. g. for the hydrolytic hydrogenation of starch, dextrin andmaltose to'sorbitol and of sacchar'os'e'to sorbitol and mannitol etc.

It is known that the hydrolytic hydrogenation of carbohydrates ispromoted by using an acid medium.

When carrying out the said process on an'industrial scal it ispractically necessary to use metal apparatus, since the hydrolytichydrogenation of carbohydrates as a rule is carried out in closedreaction chambers at temperatures above 100 C., i. e. under pressure. Asthe metal used must also be resistant to acid, the choice of thematerial is a very limited one. Apparatus made of chromium nickel steelfor instance is suitable for the purpose.

In the installations hitherto used it was desirable, particularly in thecase of a continuous hydrolytic hydrogenation process, to manufacturenot only the reaction chambers, but also other parts of theinstallation, such as the mixing or feeding vessels, the feed pumps andth feeding lines, of a metal which is resistant to acids.

The invention relates to a process for the hydrolytic hydrogenation ofcarbohydrates, which is characterized in-that the acid reaction requiredfor the conversion of the reaction mixture. is obtained by the additionof a substance, having a substantially neutral reaction at normaltemperature, but which, at the temperature required for '7 Claims. (Cl.260-635) 2. Substances which will present a neutral re; action at normaltemperature, but which at elevated temperatures will hydrolyse in anaqueous medium to substances, having an acid reaction. Examples of suchsubstances are salts of sulphuric acid estersobtained from alkenes oralcohols, such as sodium hexylsulphate. Another substance which maybeused is antimonous oxychloride, SibOCl. 9

The amount of the substance or mixture ofsube. stances to be addedaccording to the invention depends on the degree of acidity produced bythe said substances under the reaction conditions and also, of course,on the nature of the materialtol be hydrolytically hydrogenated. V t

The hydrolytic hydrogenation is generally car ried out at temperaturesabove approximately 150 C. The acid concentration must not be too high,in order to prevent as much aspossible die -j terioration of thehydrogenation catalyst. V

For the hydrolytic hydrogenation of starch, or of decomposition productsthereof to sorbitol, the'method according to the invention moreover" hasthe advantage, that'secondary reactions by which other substances thansorbitol are pro-T duced, will be prevented; at the same time theconversion will proceed, much more rapidlythan without using substancesgenerating an acid me;

dium.

thereaction, will produce theacid medium requir d.

When carrying out this'process, it wil1 be sufficient that only thoseparts of th installation which are subjected to high temperatures,consist of an acid resisting material. This is chiefly the case with thereaction chambers and, if they are used, the pre-heating and coolingdevices,

which will get into touch with the hot products.

The following are examples of substances having a neutral reaction atnormal temperature, but producing an acid medium at higher temperatures:

The drawing shows an apparatus suitable for the process according to theinvention;

"The liquid to" be hydrogenated is transported, by means of the feedpump3 fiom storingtank "l, through line 2 to'the 'preheater' 4 and thenjto'.the reaction chamber 5. Before the liquid is in troduced into thepreheater it is mixed with the catalyst paste coming from tank'G and"press? 1,, while at the same time hydrogen is introduced through line8. The liquid gas mixture leaving the reaction chamber, at the upper endflows through line '9 to cooler in and from there to a separator H, inwhich the liquid and the non reacted hydrogen are separated. Thehydrogenized liquid flows into the collecting tank l2; the hydrogen isreintroduced through line l3 by means of the gas circulation pump I l.

The invention will be explained by the following example:

7 Example To a suspension of potato starch of 30% there were added 6%(calculated on the dry material) of an alkali-freenickel-kieselguhr-catalyst and 0.15% of a substance generatingphosphoric acid at an elevated temperature. The said substancegenerating phosphoric acid had been obtained by mixing 1 part by weightof diatomaceous earth; l'part by weight of phosphoric acid (calculatedasanhydrous acid) and-3 parts by weight of water, evaporating themixture until dry, heating the residue for 3 hours at a temperature of450 C., pulverizing the preparation thus obtained, washing thepulverized material with water until it shows a neutral reaction andfinally drying the same. The dry product contained about 25% of I'I3PO4-The suspension of potato starch, catalyst and acid producing substancewas continuously pumped through a reaction chamber consisting of aplurality of vertical tubes connected in series. Hydrogen was pumpedinto the lower part of the first tube under-a pressure of 150 kgJcmF.The quantity of hydrogen usedamounted to 20 volumes (at a pressure of 150 kgs/cm?) on one volume-of the suspension.

In the first reaction tube the temperature of the reaction mass wasgradually raised to 190- 200" C. and'was'maintained at that value in thesubsequent reaction tubes. The reaction prodnot was filtered in order toeliminate the catalyst. It contained 99% of sorbitol and 1% of dextrin(calculated on dry material).

A similar result will be obtained, when using instead of the substancegenerating phosphoric acid, sodium hexyl sulphate in a proportion ofaboutO.I%.

We claim: 7 A process of manufacturing poi'yhydric alcoholssubstantially consisting'o'f sorbitol by the hydrolytic hydrogenation ofpolysaccharides, which comprises producing a neutral mixture of apolysaccharide of the group consisting of starch, modified starches,dextrin and maltose,

water and 'a latent acid generating substance which at ordinarytemperature presentsa neutral reaction but at the temperature or thehydrolytic hydrogenation will hydrolyze in an aqueous medium to providean acid reaction, and contacting said mixture with hydrogen and ahydro'genatlng. catalyst at superatlnospheric pressure and at atemperature above about 150 C., but not exceeding about 200 C.

2'. A process as described in claim 1 in which the latent acidgenerating substance is a salt of a sulphuric acid ester obtained froman alk'ene.

I 3. A process as described in claim 1 in which the latent acidgenerating substance is a salt of a sulphuric acid ester obtained froman alcoholi 4. A process as described in claim' 1 in which the latentacid generating substance is antimonous oxychlo'ride.

5. A process of manufacturing polyhydric alcohols substantiallyconsisting of sorbitol by the hydrolyti'cal hydrogenation of starch,which com- 2 "iffii. j

prises producing a neutral mixture of starch, wa ter and a latent acidgenerating .substance which at ordinary temperature presents a neutralreaction, but at the temperature of the hydrolytic hydrogenation willhydrolyze in an aqueous medium to substances having an acid reaction,and contacting said mixture at a temperature of about 190-200 C. withhydrogen and a hydrogenating catalyst at superatmospheric pressure.

6. A process of manufacturing polyhydric alcohols substantiallyconsisting of sorbitol by the continuous hydrolytic hydrogenation ofpolysaccharities, which comprises producing a neutral mixture of apolysaccharide of the group consisting of starch, modified starches,dextrin and maltose, water and a latent acid generating substance whichat ordinary temperature presents a neutral reaction but at thetemperature of the hydrolytic hydrogenation will hydrolyze in an aqueousmedium to substances havingban acid reaction, andcontinuously contactingsaidmix ture with hydrogen and 'a hydrogenating cat-' alyst at'superatmospheric pressure and at a temperature above about C., but notexceed ing about 200 C.

'7. A process of manufacturing polyhydricalg cohols substantiallyconsisting of sorbitol by the continuous hydrolytic hydrogenation ofstarch,

which comprises producing a neutral mixture of starch, water and alatent acid generating'substance which at ordinary temperature presentsa neutral reaction, but at the temperature of the hydrolytichydrogenation will hydrolyze in an aqueous medium to substances havingan acid reaction, and continuously contacting said mixture at atemperature of about ISO-Q00? C. with hydrogen and a hydrogenatingcatalyst at superatmospheric pressure.

CORNELIS MARTINUS HENDRIK'KOOL. a

HENDRIK ADRIAAN vAu WESTEN. LENZE HAR'ISTRA.

' REFERENCES CITED The following references are of. record in. the

file of this patent:

UNITED STATES PATENTS Number Name Date 'j 269,779 Endemann Dec. 26, 1882536,260 Bloede Mar. 26;,1895 2,292,293 Rose Aug. '4, 1942 2,335,731Bottoms Nov. 30, 1943 2,518,235

Hartstra et al. Aug. 8, 1950 OTHER nsrsasucss;

Englis etaL: Ind. and Eng. Chem" Vol.34, No.

7, July 1942, pp. 864-67.

Sussman: Ind. and Eng. Chem, December 1 946

1. THE PROCESS OF MANUFACTURING POLYHYDRIC ALCOHOLS SUBSTANTIALLYCONSISTING OF SORBITOL BY THE HYDROLYTIC HYDROGENATION OFPOLYSACCHARIDES, WHICH COMPRISES PRODUCING A NEUTRAL MIXTURE OF APOLYSACCHARIDE OF THE GROUP CONSISTING OF STARCH, MODIFIED STARCHES,DEXTRIN AND MALTOSE, WATER AND A LATENT ACID GENERATING SUBSTANCE WHICHAT ORDINARY TEMPERATURE PRESENTS A NEUTRAL REACTION BUT AT THETEMPERATURE OF THE HY-